This invention is generally directed to hydroxygallium phthalocyanines and photoconductive imaging members thereof, and, more specifically, the present invention is directed to processes for the preparation of hydroxygallium phthalocyanines wherein in embodiments there is avoided the use of a halo, especially a chloro component, such as chlorogallium phthalocyanine and wherein water is azeotropically removed from the hydroxygallium phthalocyanine by, for example, stirring and heating in a hydrophobic solvent such as aliphatic solvents like hexane, heptane, cyclohexane, cyclopentane, esters such as propylacetate, butylacetate or ketones such as methyl isobutyl ketone, methyl isoamyl ketone, or toluene. Also, in embodiments the obtained hydroxygallium phthalocyanine is washed with an organic solvent/ammonia mixture to reduce the sulfur impurities, for example from about 3,000 parts per million to about 100 parts per million, and thereby improve the cyclic stability of the resulting photoconductive imaging member containing the washed phthalocyanine. In embodiments, the process of the present invention comprises the preparation of Type V hydroxygailium phthalocyanine which optionally comprises the formation of a precursor gallium phthalocyanine with, for example, an X-ray powder diffraction trace having peaks at Bragg angles of 7.6, 8.1, 9.7, 16.0, 18.4, 19.2, 19.9, 24.7, 25.7 and 26.2, and the highest peak at 8.1 degrees 2.THETA., prepared by the reaction of 1,3-diiminoisoindolene with gallium acetylacetonate in a suitable solvent, such as N-methylpyrrolidone, or halonaphthalene like 1-chloronaphthalene, quinoline, and the like; hydrolyzing the precursor by dissolving in a strong acid and then reprecipitating the resulting dissolved pigment in aqueous ammonia, thereby forming Type I hydroxygallium phthalocyanine; and admixing the Type I formed with a hydrophobic solvent of, for example, hexanes, including 1-hexanes and/or isomers thereof, heptane, cyclohexane, cyclopentane or esters, such as propylacetate, butylacetate, or ketones such as methyl isobutyl ketone, methyl isoamyl ketone, or toluene, and thereafter azeotropically removing water therefrom. More specifically, in embodiments the process of the present invention comprises the formation of a precursor prepared by the reaction of 1 part gallium acetylacetonate with from about 1 part to about 10 parts and preferably about 4 parts 1,3-diimiinoisoindolene in a solvent, such as quinoline, chloronaphthalene, or N-methylpyrrolidone, in an amount of from about 10 parts to about 100 parts and preferably about 19 parts, for each part of gallium acetylacetonate that is used, to provide a pigment precursor gallium phthalocyanine, which is subsequently washed with a component, such as dimethylformamide to provide the precursor gallium phthalocyanine as determined by X-ray powder diffraction, with an X-ray powder diffraction trace having peaks at Bragg angles of 7.6, 8.1, 9.7, 16.0, 18.4, 19.2, 19.9, 24.7, 25.7, and 26.2, and the highest peak at 8.1 degrees 2.THETA.; dissolving 1 weight part of the resulting gallium phthalocyanine in concentrated, about 94 percent, sulfuric acid, in an amount of from about 1 weight part to about 100 weight parts and in an embodiment about 5 weight parts, by stirring the pigment precursor gallium phthalocyanine in the acid for an effective period of time, from about 30 seconds to about 24 hours, and in an embodiment about 2 hours at a temperature of from about 0.degree. C. to about 75.degree. C., and preferably about 40.degree. C., in air or under an inert atmosphere, such as argon or nitrogen; adding the resulting mixture to a stirred organic solvent in a dropwise manner at a rate of about 0.5 milliliter per minute to about 10 milliliters per minute and in an embodiment about 1 milliliter per minute to a nonsolvent, which can be a mixture comprised of from about 1 volume part to about 10 volume parts and preferably about 4 volume parts of concentrated aqueous ammonia solution (14.8N) and from about 1 volume part to about 10 volume parts, and preferably about 7 volume parts of water, for each volume part of acid like sulfuric acid that was used, which solvent mixture was chilled to a temperature of from about -25.degree. C. to about 10.degree. C. and in an embodiment about -5.degree. C. while being stirred at a rate sufficient to create a vortex extending to the bottom of the flask containing the solvent mixture; isolating the resulting blue pigmen t by, for example, filtration; and washing the hydroxygallium phthalocyanine product obtained with deionized water by redispersing and filtering from portions of deionized water, which portions are from about 10 volume parts to about 400 volume parts and in an embodiment about 200 volume parts for each weight part of precursor pigment gallium phthalocyanine which was used. The product, a dark blue solid, was confirmed to be Type I hydroxygallium phthalocyanine on the basis of its X-ray diffraction pattern having major peaks at 6.9, 13.1, 16.4, 21.0, 26.4, and the highest peak at 6.9 degrees 2.THETA.. The Type I hydroxygallium phthalocyanine product obtained as a wet cake, approximately 10 percent by weight pigment and 90 percent by weight water, can then be dried by azeotropically distilling off water with a hydrophobic solvent, such as hexane, of from 1 part to 30 parts of wet cake to 100 parts by volume of solvent, preferably 20 parts. Water is removed by heating to the azeotrope boiling point and continued until the distillate temperature reaches the boiling point of the hydrophobic solvent. The advantages of this method are, for example, that drying of the pigment consumes from 1 to 5 hours versus, for example, greater than 24 hours under vacuum by conventional means. Furthermore, the particle size remains in the range of 150 to 300 nanometers, as measured by TEM. Also, in embodiments the obtained crude hydroxy gallium phthalocyanine can be washed to reduce the sulfur content. The sulfur reduction washes can be accomplished on either the Type I hyrdoxygallium phthalocyanine or on the Type V hydroxy gallium phthalocyanine product. In the situation with sulfur reduction of the Type I hydroxygallium phthalocyanine, 1 part pigment to 10 parts pigment, preferably 5 parts pigment is redispersed in a hydrophilic solvent of, for example, N-methylpyrrolidone, tetrahydrofuran, acetone, methanol, isopropanol and N-N-dimethylformamide, from 100 parts solvent to 1,000 parts solvent, and preferably 300 parts. Subsequently, concentrated ammonium hydroxide (38 percent NH.sub.4 OH) solution is added, from 50 parts to 600 parts, and preferably 100 parts. The resulting dispersion is stirred for from 1 minute to 24 hours, and preferably 2 hours, and then filtered through a ceramic Buchner funnel using GFF/F filter paper. The organic solvent/aqueous base washing step is repeated 1 to 4 times, and preferably 1, and then the Type I hydroxygallium phthalocyanine is washed with deionized water until the filtrate conductivity is below from 0.1 to 20 milliSiemens per centimeter squared. The wet Type I hydroxygailium phthalocyanine pigment can than be dried azeotropically and then converted to Type V hydrogallium phthalocyanine by stirring in N-N-dimethylformamide 1 part Type pigment to 15 parts solvent.
The sulfur reduction can also be accomplished after conversion to the Type V hydroxy gallium phthalocyanine by filtering the N-N-dimethylformamide solution, redispersing the Type V hydroxygallium phthalocyanine, from 1 part to 10 parts, and preferably 5 parts in a hydrophilic solvent, such as N-N-dimethylformamide, from 100 parts solvent to 1,000 parts solvent, and preferably 300 parts. Thereafter, concentrated ammonium hydroxide solution is added, from 50 parts to 600 parts, preferably 100 parts. The resulting dispersion is stirred for from 1 minute to 24 hours, and preferably 2 hours, and then filtered. The organic solvent/aqueous base washing step is repeated from 1 to 4 times, and preferably 1 time, and then the Type V hydroxygallium phthalocyanine is washed with deionized water, to remove any ionic components, until the filtrate conductivity is from about 0.1 to about 20 milliSiemens per centimeter squared. The aqueous dispersion comprised of Type V hydroxygallium phthalocyanine, 5 parts, and 300 parts of water are filtered and then the Type V pigment is dried to provide Type V hydroxy gallium phthalocyanine. One advantage of low sulfur is reflected in superior performance of a resulting photoreceptor device. Better cycling stability of from 5 to 30 volts in 100,000 cycles is achieved and longer bench life for P/R devices results when Type V hydroxy gallium phthalocyanine with sulfur content from 25 to 200 ppm is used. The sulfur content in the product obtained was measured using a LECO SC 132 sulfur determinator. The sulfur can be burned in a furnace and detected by an infrared cell.
Advantages of the present invention in embodiments thereof include the use of an air stable reagent, gallium acetylacetonate, used in the reaction, in place of the highly reactive component gallium chloride, and the generation of a pigment precursor gallium phthalocyanine with an X-ray powder diffraction trace having peaks at Bragg angles of 7.6, 8.1,9.7, 16.0, 18.4, 19.2, 19.9, 24.7, 25.7, and 26.2, and the highest peak at 8.1 degrees 2.THETA., which when converted to the product hydroxygallium phthalocyanine Type V, by the processes described in Examples VI and VII, is free of chlorine, as opposed to the process described in Example V, whereby there is generated a pigment precursor chlorogallium phthalocyanine with an X-ray powder diffraction trace having peaks at Bragg angles of 9.1, 11.0, 18.8, 20.3, and 27.0, and the highest peak at 27.0 degrees 2.THETA., which, when converted to product hydroxygallium phthalocyanine Type V, by the processes described in Examples VI and VII, has residual chlorine levels of, for example, 0.68 percent. It is believed that impurities, such as chlorine, in the photogenerating Type V hydroxygallium phthalocyanine can cause a reduction in the xerographic performance thereof, and in particular, increased levels of dark decay, and such impurities have a negative adverse impact on the cycling performance of the photoreceptor device. Further, in embodiments there can be selected as a reactant an alkoxy gallium phthalocyanine dimer, reference copending patent application U.S. Ser. No. 233,834, U.S. Pat. No. 5,466,796 and U.S. Pat. No. 5,456,998.
The Type V obtained can be selected as organic photogenerator pigments in layered photoresponsive imaging members with charge transport layers, especially hole transport layers containing hole transport molecules such as known tertiary aryl amines. The aforementioned photoresponsive, or photoconductive imaging members can be negatively charged when the photogenerating layer is situated between the hole transport layer and the substrate, or positively charged when the hole transport layer is situated between the photogenerating layer and the supporting substrate. The layered photoconductive imaging members can be selected for a number of different known imaging and printing processes including, for example, electrophotographic imaging processes, especially xerographic imaging and printing processes wherein negatively charged or positively charged images are rendered visible using toner compositions of appropriate charge polarity. In general, the imaging members are sensitive in the wavelength region of from about 550 to about 900 nanometers, and in particular, from 700 to about 850 nanometers, thus diode lasers can be selected as the light source.
In Bull. Soc. Chim. Fr., 23 (1962), there is illustrated the preparation of hydroxygallium phthalocyanine via the precursor chlorogallium phthalocyanine. The precursor chlorogallium phthalocyanine is prepared by reaction of o-cyanobenzamide with gallium chloride in the absence of solvent. O-cyanobenzamide is heated to its melting point (172.degree. C.), and to it is added gallium chloride at which time the temperature is increased to 210.degree. C. for 15 minutes, and then cooled. The solid is recrystallized out of boiling chloronaphthalene, to give purple crystals having carbon, hydrogen and chlorine analyses matching theoretical values for chlorogallium phthalocyanine. Dissolution in concentrated sulfuric acid, followed by reprecipitation in diluted aqueous ammonia, affords material having carbon, and hydrogen analyses matching theoretical values for hydroxygallium phthalocyanine.
In JPLO.221459, there are illustrated gallium phthalocyanine compounds which show the following intense diffraction peaks at Bragg Angles (2 theta +/-0.2.degree.) in the X-ray diffraction spectrum,
1- 6.7, 15.2, 20.5, 27.0 PA1 2- 6.7, 13.7, 16.3, 20.9, 26.3 (hydroxygallium phthalocyanine Type I) PA1 3- 7.5, 9.5, 11.0, 13.5, 19.1, 20.3, 21.8, 25.8, 27.1, 33.0 (chlorogallium phthalocyanine Type I). PA1 1- 6.7, 15.2, 20.5, 27.0 PA1 2- 6.7, 13.7, 16.3, 20.9, 26.3
Further, there is illustrated in JPLO.221459 a photoreceptor for use in electrophotography comprising a charge generation material and charge transport material on a conductive substrate, and the charge generation material comprising one or a mixture of two or more of gallium phthalocyanine compounds which show the following intense diffraction peaks at Bragg angles (2 theta +/-0.2.degree.) in the X-ray diffraction spectrum,
3- 7.5,9.5, 11.0, 13.5, 19. 1,20. 3,21. 8,25. 8,27. 1,33.0.
In Konica Japanese 64-17066/89, there is disclosed, for example, the use of a new crystal modification of titanyl phthalocyanine (TiOPc) prepared from alpha-type TiOPc (Type II) by milling it in a sand mill with salt and polyethylene glycol. This publication also discloses that this new polymorph differs from alpha-type pigment in its light absorption and shows a maximum absorbance at 817 nanometers while the alpha-type exhibits a maximum at 830 nanometers. The Konica publication also discloses the use of this new form of TiOPc in a layered electrophotographic device having high photosensitivity at exposure radiation of 780 nanometers. Further, this new polymorph of TiOPc is also described in U.S. Pat. No. 4,898,799 and in a paper presented at the Annual Conference of Japan Hardcopy in July 1989. In this paper, this same new polymorph is referred to as Type y, and reference is also made to Types I, II, and III as A, B, and C, respectively.
Layered photoresponsive imaging members have been described in a number of U.S. Patents, such as U.S. Pat. No. 4,265,900, the disclosure of which is totally incorporated herein by reference, wherein there is illustrated an imaging member comprised of a photogenerating layer, and an aryl amine hole transport layer. Examples of photogenerating layer components include trigonal selenium, metal phthalocyanines, vanadyl phthalocyanines, and metal free phthalocyanines. Additionally, there is described in U.S. Pat. No. 3,121,006 a composite xerographic photoconductive member comprised of finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. The binder materials disclosed in the '006 patent comprise a material which is incapable of transporting for any significant distance injected charge carriers generated by the photoconductive particles.
The use of certain perylene pigments as photoconductive substances is also known. There is thus described in Hoechst European Patent Publication 0040402, DE3019326, filed May 21, 1980, the use of N,N'-disubstituted perylene-3,4,9,10-tetracarboxyldiimide pigments as photoconductive substances. Specifically, there is, for example, disclosed in this publication N,N'-bis(3-methoxypropyl)perylene-3,4,9,10-tetracarboxyldiimide dual layered negatively charged photoreceptors with improved spectral response in the wavelength region of 400 to 700 nanometers. A similar disclosure is revealed in Ernst Gunther Schlosser, Journal of Applied Photographic Engineering, Vol. 4, No. 3, page 118 (1978). There are also disclosed in U.S. Pat. No. 3,871,882 photoconductive substances comprised of specific perylene-3,4,9,10-tetracarboxylic acid derivative dyestuffs. In accordance with the teachings of this patent, the photoconductive layer is preferably formed by vapor depositing the dyestuff in a vacuum. Also, there are specifically disclosed in this patent dual layer photoreceptors with perylene-3,4,9,10-tetracarboxylic acid diimide derivatives, which have spectral response in the wavelength region of from 400 to 600 nanometers. Also, in U.S. Pat. No. 4,555,463, the disclosure of which is totally incorporated herein by reference, there is illustrated a layered imaging member with a chloroindium phthalocyanine photogenerating layer. In U.S. Pat. No. 4,587,189, the disclosure of which is totally incorporated herein by reference, there is illustrated a layered imaging member with a perylene pigment photogenerating component. Both of the aforementioned patents disclose an aryl amine component as a hole transport layer.
In copending application U.S. Ser. No. 537,714, the disclosure of which is totally incorporated herein by reference, there are illustrated photoresponsive imaging members with photogenerating titanyl phthalocyanine layers prepared by vacuum deposition. It is indicated in this copending application that the imaging members comprised of the vacuum deposited titanyl phthalocyanines and aryl amine hole transporting compounds exhibit superior xerographic performance with low dark decay characteristics and high photosensitivity, particularly in comparison to several prior art imaging members prepared by solution coating or spray coating, reference for example U.S. Pat. No. 4,429,029 mentioned hereinbefore.
In U.S. Pat. No. 5,153,313, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of phthalocyanine composites which comprises adding a metal-free phthalocyanine, a metal phthalocyanine, a metalloxy phthalocyanine or mixtures thereof to a solution of trifluoroacetic acid and a monohaloalkane; adding to the resulting mixture a titanyl phthalocyanine; adding the resulting solution to a mixture that will enable precipitation of said composite; and recovering the phthalocyanine composite precipitated product.
In U.S. Pat. No. 5,166,339, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of titanyl phthalocyanine which comprises the reaction of titanium tetrapropoxide with diiminoisoindolene in N-methylpyrrolidone solvent to provide Type I, or .beta.-type titanyl phthalocyanine as determined by X-ray powder diffraction analysis; dissolving the resulting titanyl phthalocyanine in a mixture of trifluoroacetic acid and methylene chloride; adding the resulting mixture to a stirred organic solvent, such as methanol, or to water; separating the resulting precipitate by, for example, vacuum filtration through a glass fiber paper in a Buchner funnel; and washing the titanyl phthalocyanine product. Examples of titanyl phthalocyanine reactants that can be selected in effective amounts of, for example, from about 1 weight percent to about 40 percent by weight of the trifluoroacetic acidic solvent mixture include known available titanyl phthalocyanines; titanyl phthalocyanines synthesized from the reaction of titanium halides such as titanium trichloride, titanium tetrachloride or tetrabromide, titanium tetraalkoxides such as titanium tetra-methoxide, -ethoxide, -propoxide, -butoxide, -isopropoxide and the like; and other titanium salts with compounds such as phthalonitrile and diiminoisoindolene in solvents such as 1-chloronaphthalene, quinoline, N-methylpyrrolidone, and alkylbenzenes such as xylene at temperatures of from about 120.degree. to about 300.degree. C.; specific polymorphs of titanyl phthalocyanine such as Type I, II, III, and IV, the preparation of which, for example, is described in the literature; or any other suitable polymorphic form of TiOPc; substituted titanyl phthalocyanine pigments having from 1 to 16 substituents attached to the outer ring of the compound, said substituent being, for example, halogens such as chloro-, bromo-, iodo- and fluoro-, alkyls with from 1 to about 6 carbon atoms such as methyl-, ethyl-, propyl-, isopropyl-, butyl-, pentyl-, and hexyl-; nitro, amino, alkoxy and alkylthio, such as methoxy-, ethoxy- and propylthio-groups; and mixtures thereof.
Disclosed in U.S. Pat. No. 5,164,493 is a process for the preparation of titanyl phthalocyanine Type I which comprises the addition of titanium tetraalkoxide in a solvent to a mixture of phthalonitrile and a diiminoisoindolene, followed by heating. The disclosure of this application is totally incorporated herein by reference. Disclosed in U.S. Pat. No. 5,189,156 is a process for the preparation of titanyl phthalocyanine Type I which comprises the reaction of titanium tetraalkoxide and diiminoisoindolene in the presence of a halonaphthalene solvent; and U.S. Pat. No. 5,206,359 is a process for the preparation of titanyl phthalocyanine which comprises the treatment of titanyl phthalocyanine Type X with a halobenzene, the disclosures of which are totally incorporated herein by reference.
Illustrated in U.S. Pat. No. 5,382,493, the disclosure of which is totally incorporated herein by reference, are processes for the preparation of Type II dihydroxygermanium phthalocyanine, which comprises the reaction of phthalonitrile or diiminoisoindolene with tetrahalogermanium or tetraalkoxygermanium in a suitable solvent, treatment of the resultant dihalogermanium phthalocyanine or dialkoxygermanium phthalocyanine intermediate with concentrated sulfuric acid, and then water, and filtering and washing of the dihydroxygermanium phthalocyanine precipitate with water using care that the filtrate of the washing does not exceeds a pH of 1.0, removing the absorbed acid on the dihydroxygermanium phthalocyanine product with an organic base, such as amine, and optionally washing the pigment crystals with an aprotic organic solvent, such as an alkylene halide like methylene chloride, tetrahydrofuran, or dimethylformamide; and the preparation of Type II dihydroxygermanium phthalocyanine by polymorphic conversion from other polymorphs, such as Type I polymorph, by simply treating with concentrated sulfuric acid, followed by the same washing processes as described above. The different polymorphic forms of dihydroxygermanium phthalocyanine can be readily identified by various known analytical methods including solid state absorption spectra and X-ray powder diffraction analysis (XRPD).
Also, in U.S. Pat. No. 5,473,064, the disclosure of which is totally incorporated herein by reference, there is illustrated a process for the preparation of hydroxygallium phthalocyanine Type V, essentially free of chlorine, whereby a pigment precursor Type I chlorogallium phthalocyanine is prepared by reaction of gallium chloride in a solvent such as N-methylpyrrolidone, present in an amount of from about 10 parts to about 100 parts, and preferably about 19 parts, with 1,3-diiminoisoindolene (DI.sup.3), in an amount of from about 1 part to about 10 parts, and preferably about 4 parts DI.sup.3, for each part of gallium chloride that is reacted; hydrolyzing said pigment precursor chlorogallium phthalocyanine Type I by standard methods, for example acid pasting, whereby the pigment precursor is dissolved in concentrated sulfuric acid and then reprecipitated in a solvent, such as water, or a dilute ammonia solution, for example, from about 10 to about 15 percent; and subsequently treating the resulting hydrolyzed pigment hydroxygallium phthalocyanine Type I with a solvent, such as N,N-dimethylformamide, present in an amount of from about 1 volume part to about 50 volume parts and preferably about 15 volume parts, for each weight part of pigment hydroxygallium phthalocyanine that is used by, for example, ball milling said Type I hydroxygallium phthalocyanine pigment in the presence of spherical glass beads, approximately 1 millimeters to 5 millimeters in diameter, at room temperature, about 25.degree. C., for a period of from about 12 hours to about 1 week, and preferably about 24 hours such that there is obtained a hydroxygallium phthalocyanine Type V, ball milling contains very low levels of residual chlorine of from about 0.001 percent to about 0.1 percent, and in an embodiment about 0.03 percent of the weight of the Type V hydroxygallium pigment, as determined by elemental analysis.
The disclosures of all of the aforementioned publications, laid open applications, copending applications and patents are totally incorporated herein by reference.